The invention relates to a system for recording and reproducing binary data by utilizing an analog magnetic recording and reproducing apparatus, in particular, to an analog magnetic recording system which may be used in a magnetic recording of binary data as are used in a solid state digital logic processor such as a microprocessor.
An analog magnetic recorder, or so-called audio tape recorder, is extensively offered for use in the recording and the reproduction of conversations, learning services, songs and performance of musical instruments, and is currently popular in home applications. Some of the features of such a recorder are the compactness, the low price and the ease of tape handling.
On the other hand, a variety of equipment and instruments incorporate a varying degree of sophisticated control by utilizing data stored in semiconductor memories of a microcomputer or the like. By way of example, in an electronic sewing machine, the main control comprises a microcomputer or other logic IC to allow a patterned sewing operation in accordance with sewing operation control data stored in a semiconductor memory. Where control data is previously stored in a semiconductor read only memory (ROM), there is a difficulty since the patterns which can be achieved by an automatic sewing operation are limited and cannot be altered. Where a read-write memory (RAM) is used, the data stored is not fixed, but it is necessary to enter sewing operation control data which is read by a card reader or tape reader. Accordingly, a recent practice is to utilize a tape cassette which is commonly used for audio purpose, as a main record medium in which sewing operation control data is previously stored. As the sewing operation proceeds, a given number of blocks of data are read from the cassette tape and written into the RAM, and the data from the RAM is read out to control the sewing operation. See, for example, pending U.S. Patent Application Ser. No. 231,089, filed Feb. 3, 1981. It will be seen that the cassette tape is compact and easy to handle, and by providing the sewing machine with an analog (audio) magnetic recording and reproducing unit, automatic pattern sewing of a high level can be achieved without involving an increased cost and while avoiding an increased size of the overall arrangement.
However, a usual cassette tape recorder or analog magnetic recording and reproducing apparatus cannot produce a playback signal which is in the form of a binary waveform if binary data is recorded. FIG. 1a shows one form of binary signal. The particular binary signal illustrated is adapted to represent signals "0" and "1" by a combination of one period of a pulse having a period of 1/2 T.sub.1 and a duty cycle of 50% (reference binary signal) and one period of a pulse having a period of T.sub.1 and a duty cycle of 50% (reference binary signal). In this manner, a time interval of 3/2 T.sub.1 is assigned to one bit of serial data. However, when such reference binary signals are recorded and reproduced by conventional analog magnetic recording and reproducing apparatus, the playback signal will be greatly distorted as indicated in FIG. 1b, presenting a difficulty in the detection of the pulse width.
Where the content of the originally recorded signal represents a digital signal comprising a succession of "1" bits followed by another digital signal comprising a succession of "0" bits, there occurs a shift in the level of the reproduced signal as indicated in FIG. 1b. In this example, the pulses representing "1" and pulses representing "0" both have an equal period, but a distinction is made therebetween by the respective duty cycles.